Recent Tsunami Research in Japan

• Hazard and risk evaluation and assessment

• Primary and secondary tsunami damage, direct and in-directdamage

• Making Tsunami Inundation Mapping through communitybased WS

• Studying on Human response and bias for the tsunamialert/warning

• Examining Reliability in Historical and more science information

• Quantitative tsunami forecast by JMA - issuing and canceling

• Lessons from the 2006 Kuril earthquake tsunami

Prof. Fumihiko Imamura

Disaster Control Research Center, Tohoku University

The Four Components of People-centred EWSystems (ISDR,2005)

Without risk assessment to estimate the past events, the EW fails.

In 2004 Indian ocean tsunami and Hurricane Katrina, the riskknowledge also failed to effectively penetrate public andpolicymaker consciousness

Risk assessment with the historical/pre-historical tsunami data isrequired. We have problem of the lack of the data/limited one.

Risk assessment Warning service

Communication Preparedness

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Evaluation of pre-historical tsunamis :Knowinghistorical and pre-historical tsunamis

• Data base and other scientific information onhistorical/pre-historical tsunamis

• Tsunami deposit / sedimentation / Ishi (stones)• New scientific information to estimate the past

tsunamis1741 Oshima-oshima, Japanese historical document

Estimated inundation area, Okinawa, Japan

■Data base on earth/tsunami with Documents/oral　tradition BC2000 - present

Only date; M and tsunami heights and human lossLimitation of area recorded, less tsunami behaviors

■Scientific data with source mechanism of faults AD1900 -present■Lack of information on the tsunami magnitude and impact on the coast

http://www.ngdc.noaa.gov/seg/hazard/tsu.shtml

The NGDC Tsunami Database contains information on tsunami events from 2000B.C. to the present in the Atlantic, Indian, and Pacific Oceans; and theMediterranean and Caribbean Seas.

Japanese documents

Historical tsunamis in documents

Damage atvillage reported

陸前国気仙郡綾里村白浜 Detail survey map attached

1896 Sanriku tsunami

inundation

Damage on houses

Direction of flow

Description ofdamage at eachvillage

Survey report

Mr.Yamana

Inundation and runup heights

runupheightinundation

height

inundationdepth

ground elevation

trace

distance from shoreline

tide levelat theevent

M.S.L.

Inundation depth

Human: killed >> 50cm

House: slightly damaged >> 1.0m

partially damaged >> 2-3.0m

totally damaged >> 3.0m

Building: damaged >> 5.0m

Tsunami height (=runup)

⇒ (ground elevation at the village)

+(Inundation height))

Runup and tidal records used for tsunami inversion: Runup data at 192 points：Tidal records at 6 stations with 10second interval (4326 data)

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欠測

Runup in meter

TokyoOita Wakayama

Check the reliability of historical data by comparison with numerical model

? Introducing the weightcoefficient in error function

Let people not forget the memory-example of picture 1896 Sanriku tsunami

Evidences of tsunamis

• Traces/marks on the land/house/trees havedisappeared for many years

• However, there are some evidences remainingfor long time and containing scientific information– Sand Sedimentation due to tsunamis resulting

tsunami layers

– Coral rocks moved by tsunamis

Minoan BC14COkinawa 1771 Indian ocean 2004

Tsunami Sedimentation(Modified after Minoura and Nakaya, 1991)

1983 Japan sea tsunami

Modified after Takada et al. (2002)

Nankai trough

AD AD

Historicalearthquake/tsunami

Tsunami deposit

The case of Tokai/Tonankai in Japan

The age of tsunami sand layers/deposit suggeststhe frequency of them at the area

200 m

T1

T12

Limit of flat and very shallowsea floor

2004 Indian ocean tsunami Impacton the coastal environment

•Large change of topography

•Coral rocks removed, tsunami ishi

•Damage on mangrove

Goto et al, 2005

Large erosion

Tsunami boulders transported by the 2004 Indian Ocean tsunami atKhao Lak, Thailand

Goto et al., (in press)

Tetra-pot transported by the tsunamis at Akita coast（1983 Nihonkai-Chubu Earthquake and tsunami）

Photo provided by K. Minoura

The position, size and weight of brockssuggest us the information the process ofrunup with wave force and hydraulics

Tsunami deposit/

Number of layers

Thickness/seize of sands

Tsunami Ishi (stone)/

Number of stones

Locations /seize of stones

Number of attacks of tsunamis

Inundation/runup-rundown

Wave force/ current

Distribution of runup along coast

Propagation process of tsunamis

Their sources mechanism

Tsunami Numerical model + forward/inversion method

Estimation of runup from the evidence

runupheight

Gap of location of evidence and runup

Green function;Wave height ?Wave period ?

Inversionanalysis

Forward analysis

Tsunami Forecasting for near and far- fieldtsunamis

Tsunami source << 600km

Started in 1952 for near- field

Started in 1965 after the 1960 Chilean tsunami

1952-1970 : 22min+10.7, 2.2/year

1971-1983 : 16 min+6.7

1983 Akita-oki 14min

1993 Okushiri 5 min, 5 /year

Now << 3 min.

quantitative

detailFrom 18 to 66 regions

A new tsunamiwarning systemstarted in 1999

Occurrence of

Earthquake

GenerationGenerationofof

TsunamiTsunami

Detectionof

Seismic Wave

Determinationof

Magnitude and Hypocenter

Evaluationof

Tsunami

Issuanceof

Tsunami Warning

Issuanceof

Tsunami Information

Detectionof

Tsunami

Network of seismographsNetwork of seismographs

System to calculate magnitude System to calculate magnitude Immediately with seismic wave dataImmediately with seismic wave data

Criteria for Tsunami grade/ Criteria for Tsunami grade/numerical simulationnumerical simulation

Communication facility to disseminateCommunication facility to disseminateTsunami Warning Tsunami Warning

Components oftsunami warning system

Real Network of tide gauge Real Network of tide gauge to monitor tsunami to monitor tsunami

What we need for Tsunami Warning; Issuing after generation

Dedicated line to transmit data in real timeDedicated line to transmit data in real time

JMA modified How people received and make action ?

How the datarevised ?

Data Assimilation

SeismologicalObservation(Location,M)

Tsunami WaveformData Base

Offshore Tsunami Observation

Improved Prediction of Tsunami Amplitude

& Travel Times

Existing Tsunami Forecast Scheme

Initial estimate

Initial estimate isimproved

Hirata(2005) modified

Sibolga

Kuraburi

KrabiAdjustment of source

location (X) & faultdislocation (D) by inversion

Kuril Island

Yamanaka(2006)

M=7.9

Strike　２２５Dip　３０Slip ９４Depth ３０ｋｍArea ２００ｋｍ×５０ｋｍDislocation　９．４ｍ

New problems in the 2006 Kuril

Topics

• Ground-quake in Japan was small• The tsunami propagated all coast facing Pacific ocean in

Japan and toward the Pacific ocean including Hawaii andwest coast

• 20:15 PM happened, 20:29 PM Tsunami warning issued• 23:31 PM and 1:30 AM cancelled (less than 50 cm in wave)• 5-6 AM damage reported and the maximum recorded• The tsunami effected for more than half day

– Direct propagation wave, edge wave and scattering wavecombined

• Only 10 % of residences could evacuate

11/16朝方に，被害を発見気仙沼市の只越漁港で3隻、石巻市の相川漁港で1隻、旧歌津町の港漁港で1隻の漁船が転覆

Three boats damaged by thetsunami 7 or 8 hours after

Fishery port, Tadakoshi

Fishery port, Aikawa

検潮記録にシミュレーション結果を重ね合わせてみました

八戸

比較的よく一致

館山

後半の成分が過小評価なのは天皇海山の反射を考慮していないため？（要確認）

recorded

computed

recordedcomputed

at Hachinohe, Honnsyhu

at Tateyama, Chiba

2.5時間後：直接波、境界波

天皇海山列Sea mounts

３時間後：海山列での反射が始まる

Tsunami analysis・linear long wave・dx=1.35km・8 hours

４時間後：散乱波の一部が日本へ

５−６時間後：散乱波が日本沿岸に到達始める

CG; DCRC, Tohoku Univ. and Alfa consultant

津波波源tsunamisource

海山列Chain ofMt sea

海溝trough

陸棚continentalshelf

直接波direct wave

散乱波Scatteringwave

散乱波Scatteringwave

直接波Directwave

境界波

境界波Edge wave

Topics

• What is criteria to cancel a warning for residence andpeople in sea ?

• Only 5 % residences could evacuate. How can we ensurethem make action for tsunami evacuation.